The FDA is warning that the antibiotic azithromycin (Zithromax, Zmax) should not be given long-term to prevent bronchiolitis obliterans in patients with cancers of the blood or lymph nodes who undergo a donor stem cell transplant. Results of a clinical trialfound an increased rate of relapse in cancers affecting the blood and lymph nodes, including death, in these patients.
Bronchiolitis obliterans syndrome is caused by inflammation and scarring in the airways of the lungs, resulting in severe shortness of breath and dry cough. Cancer patients who undergo stem cell transplants from donors are at risk for bronchiolitis obliterans syndrome. The manufacturer of brand-name azithromycin is providing a Dear Healthcare Provider letter on this safety issue to health care professionals who care for patients undergoing donor stem cell transplants. Azithromycin is not approved for preventing bronchiolitis obliterans syndrome, and there are no known effective antibiotic treatments for prophylaxis of the syndrome.
Researchers in France identified this increased risk of cancer relapse and death while conducting a clinical trial investigating the effectiveness of long-term azithromycin to prevent bronchiolitis obliterans syndrome in patients who undergo donor, or allogenic, stem cell transplants for cancers of the blood and lymph nodes. The researchers concluded that the risks of long-term azithromycin exposure after donor stem cell transplantation may exceed the benefits. The trial could not determine why the rates of cancer relapse and death were higher with azithromycin.
The researchers stopped the ALLOZITHRO1 trial approximately 13 months after the study completed enrollment of 480 patients because an unexpected increase in the rate of both cancer relapses and death was observed in patients taking azithromycin. Cancer relapse was observed in 77 patients (32.9%) with azithromycin treatment compared to 48 patients (20.8%) with placebo. A total of 95 patients died in the azithromycin treatment group versus 66 patients in the placebo group; thus, the 2-year survival rate was 56.6% in azithromycin-treated patients compared to 70.1% in those receiving a placebo.
Patients who have had a stem cell transplant should not stop taking azithromycin without first consulting with their health care professional.
Source: FDA.gov, August 3, 2018